Each proposal in this program project is concerned with cellular developmental neurobiology. The central hypothesis of these proposals is that there is a continuous interaction between the determinants of neuronal form and function, and that these interactions play an essential role in establishing the characteristics of the differentiated neuron. Although the basic analyses by these projects has been at the cellular level, there is an increased tendency to now carry these through to the molecular level. This is explicit in the application of hybridoma techniques by each of the projects. Some will use the monoclonal antibodies as labels for subsets of neurons to increase the resolution of the cellular analyses. Others will use the monoclonal antibodies to directly assist in the identification of molecules that are directly playing an important role in developmental processes. This shared interest in the cellular events occurring during the development of the nervous system and in the application of hybridoma techniques has resulted in many productive interactions and direct collaborations among all participants. Both invertebrate and vertebrate nervous systems are used in order to take advantage of specific properties of each. Those projects examining the factors controlling cell number by influencing rates of cell production or cell death will contribute to our understanding of degenerative disorders like Huntington's, Parkinson's and Alzheimer's diseases. The development of neuronal control of the endocrine system in cockroaches and identification of the neuropeptides involved will produce information useful in regulating excessive populations of insects. Some projects are studying axon growth - the effect of neuronal activity on it and the function and regulation of synthesis of molecules present in cells only during this process. Other projects study the specificity of synapse formation. Knowledge of the factors mediating axon growth and synapse formation obtained from these projects will be useful for developing more rational therapeutic treatments of neuronal damage from strokes, multiple sclerosis and direct injury.